Glucocorticoid independence of acute thymic involution induced by lymphotoxin and estrogen

[Vascular Remodeling Induced by Biological Stresses]

The thymus is a vital organ for functional immune systems, and is the site of T cell development, which plays a central role in cellular immune defenses. Unlike other major organs, the thymus is highly dynamic in size and structure. It shrinks immediately upon bacterial infection, aging, pregnancy, mental stress, nutritional deficiency, and more. The reduction in size and function of the thymus during such biological events is called thymic involution or thymic atrophy; thymic involution is a particularly important issue because dysfunctional T cell immunity increases the risks of tumorigenesis and infectious diseases. However, the molecular mechanisms underlying thymic involution remain obscure. Our recent study indicated that blood vessels are remodeled during thymic involution that occurs upon aging, estradiol-treatment, or nutritional deficiency. We also found that prostanoid synthesis is induced during thymic involution. Treatment with non-steroidal anti-inflammatory drugs (NSAIDs), aspirin or etodolac, at least partially inhibited thymic involution-induced remodeling of the blood vessels, suggesting that prostanoids are involved in blood vessel remodeling. Our results revealed the potential role of blood vessel remodeling during thymic involution, which can lead to biological stress-induced immunosenescence.

Sex Hormones in Acquired Immunity and Autoimmune Disease

Women have stronger immune responses to infections and vaccination than men. Paradoxically, the stronger immune response comes at a steep price, which is the high incidence of autoimmune diseases in women. The reasons why women have stronger immunity and higher incidence of autoimmunity are not clear. Besides gender, sex hormones contribute to the development and activity of the immune system, accounting for differences in gender-related immune responses. Both innate and adaptive immune systems bear receptors for sex hormones and respond to hormonal cues. This review focuses on the role of sex hormones particularly estrogen, in the adaptive immune response, in health, and autoimmune disease with an emphasis on systemic lupus erythematosus.

Immune dysregulation may contribute to disease pathogenesis in spinal muscular atrophy mice

Spinal muscular atrophy (SMA) has long been solely considered a neurodegenerative disorder. However, recent work has highlighted defects in many other cell types that could contribute to disease aetiology. Interestingly, the immune system has never been extensively studied in SMA. Defects in lymphoid organs could exacerbate disease progression by neuroinflammation or immunodeficiency. Smn depletion led to severe alterations in the thymus and spleen of two different mouse models of SMA. The spleen from Smn depleted mice was dramatically smaller at a very young age and its histological architecture was marked by mislocalization of immune cells in the Smn^2B/- model mice. In comparison, the thymus was relatively spared in gross morphology but showed many histological alterations including cortex thinning in both mouse models at symptomatic ages. Thymocyte development was also impaired as evidenced by abnormal population frequencies in the Smn^2B/- thymus. Cytokine profiling revealed major changes in different tissues of both mouse models. Consistent with our observations, we found that survival motor neuron (Smn) protein levels were relatively high in lymphoid organs compared to skeletal muscle and spinal cord during postnatal development in wild type mice. Genetic introduction of one copy of the human SMN2 transgene was enough to rescue splenic and thymic defects in Smn^2B/- mice. Thus, Smn is required for the normal development of lymphoid organs, and altered immune function may contribute to SMA disease pathogenesis.

Cytoplasm estrogen receptor β5 as an improved prognostic factor in thymoma and thymic carcinoma progression

A number of previous studies have reported that sex steroid hormones, including estrogens, are involved in the regulation of the thymic function. The aim of the present study was to investigate the expression of estrogen receptor β5 (ERβ5) in thymic tumors and the correlation between ERβ5 expression and thymoma biological characteristics. The expression levels of ERβ5 in thymic epithelial tumors was evaluated in 103 patents using immunohistochemical staining and reverse transcription-quantitative polymerase chain reaction. In addition, an indirect immunofluorescence assay was performed to evaluate the ERβ5 expression levels in the TC1889 and T1682 cell lines. The survival outcome was estimated using Kaplan-Meier plots. The results indicated that ERβ5 expression was mainly located in the thymic tumor cell cytoplasm (87.37%; 90/103 cases) and overexpression was observed in thymic tumors compared with normal thymic tissues (P=0.001). Using the Kruskal-Wallis test, a statistically significant association was observed between cytoplasmic ERβ5 (cERβ5) expression and thymic tumor subtypes (P=0.024) and stages (P=0.003 and R=-0.376). The Kaplan-Meier plots revealed that cERβ5 expression was significantly associated with improved overall and progression-free survival (P=0.008 and P=0.004, respectively). The present study suggested that overexpression of cERβ5 may indicate an improved prognosis and may be involved in the underlying mechanism through which estrogen inhibits thymoma and thymic carcinoma development.

Myasthenia gravis: a comprehensive review of immune dysregulation and etiological mechanisms

Autoimmune myasthenia gravis (MG) is characterized by muscle weakness caused by antibodies directed against proteins of the neuromuscular junction. The main antigenic target is the acetylcholine receptor (AChR), but the muscle Specific Kinase (MuSK) and the low-density lipoprotein receptor-related protein (LRP4) are also targets. This review summarizes the clinical and biological data available for different subgroups of patients, who are classified according to antigenic target, age of onset, and observed thymic abnormalities, such as follicular hyperplasia or thymoma. Here, we analyze in detail the role of the thymus in the physiopathology of MG and propose an explanation for the development of the thymic follicular hyperplasia that is commonly observed in young female patients with anti-AChR antibodies. The influence of the pro-inflammatory environment is discussed, particularly the role of TNF-α and Th17-related cytokines, which could explain the escape of thymic T cells from regulation and the chronic inflammation in the MG thymus. Together with this immune dysregulation, active angiogenic processes and the upregulation of chemokines could promote thymic follicular hyperplasia. MG is a multifactorial disease, and we review the etiological mechanisms that could lead to its onset. Recent global genetic analyses have highlighted potential susceptibility genes. In addition, miRNAs, which play a crucial role in immune function, have been implicated in MG by recent studies. We also discuss the role of sex hormones and the influence of environmental factors, such as the viral hypothesis. This hypothesis is supported by reports that type I interferon and molecules mimicking viral infection can induce thymic changes similar to those observed in MG patients with anti-AChR antibodies.

Accelerated thymic atrophy as a result of elevated homeostatic expression of the genes encoded by the TNF/lymphotoxin cytokine locus

TNF, lymphotoxin (LT)-alpha, LT-beta and LIGHT are members of a larger superfamily of TNF-related cytokines that can cross-utilize several receptors. Although LIGHT has been implicated in thymic development and function, the role of TNF and LT remains incompletely defined. To address this, we created a model of modest homeostatic overexpression of TNF/LT cytokines using the genomic human TNF/LT locus as a low copy number Tg. Strikingly, expression of Tg TNF/LT gene products led to profound early thymic atrophy characterized by decreased numbers of thymocytes and cortical thymic epithelial cells, partial block of thymocyte proliferation at double negative (DN) 1 stage, increased apoptosis of DN2 thymocytes and severe decline of T-cell numbers in the periphery. Results of backcrossing to TNFR1-, LTbetaR- or TNF/LT-deficient backgrounds and of reciprocal bone marrow transfers implicated both LT-alpha/LT-beta to LTbetaR and TNF/LT-alpha to TNFR1 signaling in accelerated thymus degeneration. We hypothesize that chronic infections can promote thymic atrophy by upregulating LT and TNF production.

Overexpression of lymphotoxin in T cells induces fulminant thymic involution

Activated lymphocytes and lymphoid-tissue inducer cells express lymphotoxins (LTs), which are essential for the organogenesis and maintenance of lymphoreticular microenvironments. Here we describe that T-cell-restricted overexpression of LT induces fulminant thymic involution. This phenotype was prevented by ablation of the LT receptors tumor necrosis factor receptor (TNFR) 1 or LT beta receptor (LTbetaR), representing two non-redundant pathways. Multiple lines of transgenic Ltalphabeta and Ltalpha mice show such a phenotype, which was not observed on overexpression of LTbeta alone. Reciprocal bone marrow transfers between LT-overexpressing and receptor-ablated mice show that involution was not due to a T cell-autonomous defect but was triggered by TNFR1 and LTbetaR signaling to radioresistant stromal cells. Thymic involution was partially prevented by the removal of one allele of LTbetaR but not of TNFR1, establishing a hierarchy in these signaling events. Infection with the lymphocytic choriomeningitis virus triggered a similar thymic pathology in wt, but not in Tnfr1(-/-) mice. These mice displayed elevated TNFalpha in both thymus and plasma, as well as increased LTs on both CD8(+) and CD4(-)CD8(-) thymocytes. These findings suggest that enhanced T cell-derived LT expression helps to control the physiological size of the thymic stroma and accelerates its involution via TNFR1/LTbetaR signaling in pathological conditions and possibly also in normal aging.

GPR30 contributes to estrogen-induced thymic atrophy

The mechanisms by which prolonged estrogen exposures, such as estrogen therapy and pregnancy, reduce thymus weight, cellularity, and CD4 and CD8 phenotype expression, have not been well defined. In this study, the roles played by the membrane estrogen receptor, G protein-coupled receptor 30 (GPR30), and the intracellular estrogen receptors, estrogen receptor alpha (ERalpha) and beta (ERbeta), in 17beta-estradiol (E2)-induced thymic atrophy were distinguished by construction and the side-by-side comparison of GPR30-deficient mice with ERalpha and ERbeta gene-deficient mice. Our study shows that whereas ERalpha mediated exclusively the early developmental blockage of thymocytes, GPR30 was indispensable for thymocyte apoptosis that preferentially occurs in T cell receptor beta chain(-/low) double-positive thymocytes. Additionally, G1, a specific GPR30 agonist, induces thymic atrophy and thymocyte apoptosis, but not developmental blockage. Finally, E2 treatment attenuates the activation of nuclear factor-kappa B in CD25(-)CD4(-)CD8(-) double-negative thymocytes through an ERalpha-dependent yet ERbeta- and GPR30-independent pathway. Differential inhibition of nuclear factor-kappaB by ERalpha and GPR30 might underlie their disparate physiological effects on thymocytes. Our study distinguishes, for the first time, the respective contributions of nuclear and membrane E2 receptors in negative regulation of thymic development.

The complex role of estrogens in inflammation

There is still an unresolved paradox with respect to the immunomodulating role of estrogens. On one side, we recognize inhibition of bone resorption and suppression of inflammation in several animal models of chronic inflammatory diseases. On the other hand, we realize the immunosupportive role of estrogens in trauma/sepsis and the proinflammatory effects in some chronic autoimmune diseases in humans. This review examines possible causes for this paradox. This review delineates how the effects of estrogens are dependent on criteria such as: 1) the immune stimulus (foreign antigens or autoantigens) and subsequent antigen-specific immune responses (e.g., T cell inhibited by estrogens vs. activation of B cell); 2) the cell types involved during different phases of the disease; 3) the target organ with its specific microenvironment; 4) timing of 17beta-estradiol administration in relation to the disease course (and the reproductive status of a woman); 5) the concentration of estrogens; 6) the variability in expression of estrogen receptor alpha and beta depending on the microenvironment and the cell type; and 7) intracellular metabolism of estrogens leading to important biologically active metabolites with quite different anti- and proinflammatory function. Also mentioned are systemic supersystems such as the hypothalamic-pituitary-adrenal axis, the sensory nervous system, and the sympathetic nervous system and how they are influenced by estrogens. This review reinforces the concept that estrogens have antiinflammatory but also proinflammatory roles depending on above-mentioned criteria. It also explains that a uniform concept as to the action of estrogens cannot be found for all inflammatory diseases due to the enormous variable responses of immune and repair systems.

Maternal microchimerism leads to the presence of interleukin-2 in interleukin-2 knock out mice: implications for the role of interleukin-2 in thymic function

The role of interleukin-2 (IL-2) in thymic development is uncertain. Not surprisingly, IL-2 knockout (KO) mice have been used to address this question. However, as we report here, such mice are chimeric, containing both IL-2 KO cells and IL-2-expressing cells transferred in utero from their heterozygous mothers. These cells produce IL-2 in amounts detectable by conventional means, and their presence in lymphoid tissues confounds efforts to define the true IL-2 KO phenotype. To minimize the amount of IL-2 available to the thymus, we subjected recombinase activating gene-1 KO mice to bone marrow transplantation using IL-2 KO donors, and then followed the reconstitution of the thymus. The thymuses of these mice became increasingly aberrant over time, including abnormalities in both stromal cells and thymocytes. These results demonstrate that IL-2 is critical to several aspects of thymic function, a finding previously obscured by the presence of IL-2 in IL-2 KO mice.

Cellular mechanism of thymic involution

Involution of the thymus and alterations in the development of thymocytes are the most prominent features of age-related immune senescence. We have carried out a comparative analysis of thymocyte and stroma in rapid thymic involution DBA/2 (D2) strain of mice compared with slow involution C57BL/6 (B6) strain of mice. Analysis of mice at 15 months of age suggested an age-related decrease in the thymocyte cell count, a block in the development of T cells and cortical involution in D2 mice compared with 3-month-old mice. TUNEL (terminal-deoxynucleotidyl-transferase-mediated dUTP-digoxigenin nick end labelling) staining and fluorescence-activated cell sorter (FACS) analysis showed that there was a significant increase in apoptotic cells in the cortex region of thymus in 15-month-old D2 mice compared with the same aged B6 mice. The thymocyte proliferation rate, as assessed by bromodeoxyuridine (BrdU) staining and [3H]-thymidine incorporation assay, was lower in 3-month-old D2 mice compared with the same age B6 mice. Immunohistochemical staining showed that the arrangement of MTS (mouse thymus stromal)-10+ epithelial cells and MTS-16+ connective tissue staining pattern had become disorganized in 15-month-old D2 mice but remained intact in B6 mice of the same age. These results suggest that, in D2 mice, both the thymocytes and stromal cells exhibit age-related defects, and that the genetic background of mice plays an important role in determining age-related alterations in thymic involution.

Immunomodulation by diethylstilbestrol is dose and gender related: effects on thymocyte apoptosis and mitogen-induced proliferation

It is believed, but not proven, that the immunomodulatory effects of DES may vary with the dose and/or gender. To address these critical gaps in the literature, diethylstilbestrol (DES) was administered to female and male CD-1 mice as four subcutaneous injections for 1 week at 0, 5, 15, and 30 microg/kg bw doses, and immunological and reproductive effects examined a day after the last injection. Female thymuses were significantly larger than their male counterparts. Short-term administration of DES to female or male mice neither induced thymic atrophy nor altered the relative percentages of thymic subsets. Nevertheless, DES treatment of female or male mice induced a dose-related apoptosis of CD4(+)8(+), CD4(+)8(-) and CD4(-)8(+) subsets as analyzed by 7-amino-actinomycin D (7-AAD). Immature CD4(-)8(-) subset of thymocytes from females was also affected by high dose DES. The pattern of mitogen-induced proliferation of splenic lymphocytes varied with the dose of hormone and the gender. In females, splenic lymphocytes from low dose DES (5 microg/kg bw)-treated mice exhibited an increased proliferative response to Con-A, LPS or PMA/ionomycin compared with controls. Similar cultures from mice treated with higher doses of DES (15 or 30 microg/kg bw) did not manifest an increased proliferative response, but rather showed a trend for suppressed proliferation, especially in response to Con-A. In males, DES had minimal effects with the exception of increased proliferative response to Con-A in splenocytes from medium-dose-DES-treated mice. The changes in mitogen-induced proliferation in DES-treated female mice were not mirrored by similar changes in the relative numbers of CD90(+) or CD45R(+) cells, or in ratios of anti-apoptotic Bcl-2 to apoptotic Bax proteins. Con-A-activated splenocytes from DES-treated mice, particularly from females, had a decreased ability to secrete interferon-gamma compared with controls. Taken together, these findings suggest that short-term exposure to DES has differential immunological effects depending upon the dose of hormone and sex.

Evidence for estradiol-induced apoptosis and dysregulated T cell maturation in the thymus

In an attempt to delineate the immunological alterations that may occur following treatment with estrogen, groups of C57BL/6 mice were treated with 75mg/kg body weight of beta-estradiol-17-valerate (E2) or the vehicle. The thymus from these mice were harvested on days 1, 4 and 7 following treatment. The thymocytes from E2-treated mice when cultured in vitro for 24h, showed increased levels of apoptosis when compared to controls. The apoptosis was demonstrable by both TUNEL assay and AnnexinV/propidium iodide (PI) staining. Also, thymic atrophy and increased apoptosis of thymocytes when cultured in vitro were seen when lower doses of E2 (5mg/kg) were administered. The thymus from E2-treated mice on days 4 and 7 also showed a decrease in the percentage of CD4(+)CD8(+) (DP) T cells and an increase in the percentage of CD4(-)CD8(-) (DN), CD4(+) and CD8(+) T cells. However, the total cellularity of all T cell subsets in the thymus was decreased following E2 treatment. Earlier studies from our laboratory and elsewhere have demonstrated that in thymocytes undergoing apoptosis, there is increased expression of surface markers including CD3, alphabetaTCR and CD44 with a simultaneous decrease in the expression of J11d. Similar changes were observed in thymocytes from mice on days 4 and 7 following E2 treatment. These data therefore confirmed that the thymocytes were indeed undergoing apoptosis following E2 treatment. Together, our studies suggest for the first time that estrogen may induce thymic atrophy by triggering apoptosis.

Neuroendocrine control of thymus physiology

The thymus gland is a central lymphoid organ in which bone marrow-derived T cell precursors undergo differentiation, eventually leading to migration of positively selected thymocytes to the peripheral lymphoid organs. This differentiation occurs along with cell migration in the context of the thymic microenvironment, formed of epithelial cells, macrophages, dendritic cells, fibroblasts, and extracellular matrix components. Various interactions occurring between microenvironmental cells and differentiating thymocytes are under neuroendocrine control. In this review, we summarize data showing that thymus physiology is pleiotropically influenced by hormones and neuropeptides. These molecules modulate the expression of major histocompatibility complex gene products by microenvironmental cells and the extracellular matrix-mediated interactions, leading to enhanced thymocyte adhesion to thymic epithelial cells. Cytokine production and thymic endocrine function (herein exemplified by thymulin production) are also hormonally controlled, and, interestingly in this latter case, a bidirectional circuitry seems to exist since thymic-derived peptides also modulate hormonal production. In addition to their role in thymic cell proliferation and apoptosis, hormones and neuropeptides also modulate intrathymic T cell differentiation, influencing the generation of the T cell repertoire. Finally, neuroendocrine control of the thymus appears extremely complex, with possible influence of biological circuitry involving the intrathymic production of a variety of hormones and neuropeptides and the expression of their respective receptors by thymic cells.

Effects of Kampo medicine, Toki-shakuyaku-san (Tang-Kuei-Shao-Yao-San), on choline acetyltransferase activity and norepinephrine contents in brain regions, and mitogenic activity of splenic lymphocytes in ovariectomized mice

We investigated the effects of Toki-shakuyaku-san (TSS, Tang-Kuei-Shao-Yao-San in Chinese), Japanese traditional herbal medicine, on the nervous and immune systems in ovariectomized mice as a climacteric disorder model. Female C57BL/6 mice were ovariectomized (OVX) and TSS was given daily through the drinking water for either 10 or 20 days from the day after ovariectomy. After completion of experimental sessions, animals were sacrificed and specific brain regions were assayed for choline acetyltransferase (ChAT) activity and norepinephrine contents. The mitogenic activities, alkaline phosphatase activity and 3-(4, 5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H terazolium bromide (MTT) activity, in splenic lymphocytes has also measured. Furthermore, the effects of TSS on learning and memory ability were studied by the step-through type passive avoidance test. As the results, the administration of TSS significantly suppressed the decrease of ChAT activity in the cerebral cortex (CC) and the dorsal hippocampus (DH) of ovariectomized mice at 10 days after ovariectomy, however no significant effect was observed at 20 days after ovariectomy. Norepinephrine contents in OVX group were decreased at 10 and 20 days after ovariectomy in the CC and the ventral hippocampus (VH). The administration of TSS significantly suppressed the decrease of norepinephrine contents at 20 days after ovariectomy. The mitogenic activities of lymphocyte in spleen were increased at 10 days after ovariectomy, and decreased at 20 days after ovariectomy. However, the suppression of these changes was observed in the group given TSS. The mean latent period was also shortened in the passive avoidance test in the OVX group, but TSS treated group improved mean latency. From these observations, it is inferred that administration of TSS brings on the synthesis of acetylcholine and norepinephrine in the CC and hippocampus, and may improve the memory related behavior and the abnormalities in lymphocytes in the models of the climacteric disorder.

Effect of adrenalectomy on ethanol-associated changes in lymphocyte cell numbers and subpopulations in thymus, spleen, and gut-associated lymphoid tissues

Consumption of ethanol (ETOH) by experimental animals and human beings is associated with elevated serum levels of corticosteroids. One of the most robust findings associated with ETOH consumption is a loss of lymphocytes from thymus and spleen, as well as from peripheral lymphoid organs to include mesenteric lymph nodes and Peyer's patches, which are lymphoid organs associated with the gastrointestinal tract. To study the role of corticosteroids in loss of cells from thymus, spleen, and gut-associated lymphoid organs, adrenalectomized (ADX) or intact C57Bl/6 mice were fed a liquid diet containing ETOH (to supply 36% of calories as ETOH) or an isocaloric control diet with a pair-feeding protocol. Loss of lymphocytes from all lymphoid organs was associated closely with serum corticosterone levels in both ETOH-fed and pair-fed groups. ETOH-fed ADX animals showed much less cell loss than did ETOH-fed intact animals. However, there was still an association between ETOH consumption and cell loss when cell loss in ETOH-fed ADX animals was compared with that in ADX pair-fed and ADX chow-fed groups. In both intact and ADX animals ETOH consumption was associated with a loss of immature (CD4(+) and CD8(+)) cells from the thymus. These data lead to the suggestion that corticosteroids are responsible for most of the cell loss from thymus, spleen, mesenteric lymph nodes, and Peyer's patches in association with ETOH consumption. Some cell loss, however, is independent of corticosteroids. The data presented here also support the suggestion that cell loss from lymphoid organs could be the result of nutritional factors.

Resistance of extrathymic T cells to stress and the role of endogenous glucocorticoids in stress associated immunosuppression

When mice were exposed to restraint stress for 12 or 24 h, severe lymphopenia was induced in all immune system organs, including the liver and the thymus. However, in adrenalectomized mice, this response was completely absent. Phenotypic characterization revealed that interleukin (IL)-2Rbeta+CD3int cells (i.e. extrathymic T cells) with CD4+ phenotype and the NK1.1+ subset of CD3int cells (i.e. NKT cells) in the liver as well as the mature conventional T cells in the thymus were resistant to such stress. In adrenalectomized mice, there was no significant change in the distribution of lymphocyte subsets in all tested organs before stress. Interestingly, the number of lymphocytes in the liver and spleen and the proportion of NKT cells in the liver rather increased after stress in these adrenalectomized mice. Therefore, endogenous steroid hormones were indicated to be important in the induction of immunosuppressive states after stress. Among stress associated cytokines, the secretion of tumour necrosis factor (TNF)-alpha was completely suppressed while that of IL-6 was partially suppressed in adrenalectomized mice. These results suggest that endogenous steroid hormones are important for the induction of the stress associated immunosuppression and that NKT cells are resistant to stress, namely, resistant to exposure to endogenous steroid hormones.

Mechanisms underlying immunologic states during pregnancy: possible association of the sympathetic nervous system

NK and extrathymic T cells are abundant in the decidua of the pregnant uterus. To determine how this unique pattern is induced, overall populations of leukocytes were examined in the blood and other tissues in pregnant women. Time-kinetic studies showed that a basal change of leukocytes during pregnancy was granulocytosis and lymphocytopenia in the blood. This change might be due to sympathetic nerve activation during pregnancy, because the administration of catecholamine is known to activate myelopoiesis in the bone marrow. In addition to the numerical change, the functional activation of NK and extrathymic T cells also seemed to be present. This might be due to NK cells and extrathymic T cells (as well as granulocytes), which carry a high density of surface adrenergic receptors. Such functional activation of NK and extrathymic T cells was more prominent in the blood and urine in patients with preeclampsia and hyperemesis gravidarum than in normal pregnant women. The present results suggest that the activation of granulocytes, NK cells, and extrathymic T cells is essential for the maintenance of pregnancy but that overactivation thereof may be responsible for the onset of pregnancy disorders.

Administration of glucocorticoids markedly increases the numbers of granulocytes and extrathymic T cells in the bone marrow

Glucocorticoids, steroid hormones, are widely used as an anti-inflammatory drug. However, clinicians have sometimes encountered adverse drug reactions such as ulcers and tissue damage. In this study, we investigated how such adverse reactions of glucocorticoids are evoked, using an experimental mice model. When hydrocortisone (0.5 or 1.0 mg/day/mouse) was administered daily for 2 weeks, severe leukocytopenia was induced in all immune system organs. However, granulocytes (Gr-1(+)Mac-1(+)) were increased in number in the bone marrow and peripheral blood. This seemed to be due to an elevated level of myelopoiesis in the bone marrow. As well as increasing in number, granulocytes were functionally activated as estimated by the Ca2+ influx and superoxide production. The proportion of primordial T cells (CD3(int)IL-2Rbeta+) in the thymus and the number of primordial T cells in the bone marrow also increased. Mice administered hydrocortisone became susceptible to stress. Thus, these mice showed gastric ulcers when they were exposed to restraint stress for 12 h. These results suggest that activated granulocytes and primordial T cells might provide a mechanism involved in steroid ulcers and tissue damage, possibly through the superoxide production of granulocytes and the autoreactivity of primordial T cells.

Tumor necrosis factor-beta is associated with thymic apoptosis during acute rejection

BACKGROUND

Intrathymic events undergoing allograft rejection remain undefined. The present study investigated the role of tumor necrosis factor-beta on acute thymic involution in rat hepatic allograft recipients during rejection.

METHODS

Apoptosis and cellular phenotypic changes in the thymus were studied after hepatic transplantation.

RESULTS

Thymocytes in both the medulla and cortex were sparse during acute rejection. Phenotypically, CD4+CD8+ T cells decreased significantly, whereas there were relative increases in CD4-CD8-, CD4+CD8-, and CD4-CD8+ T cells in untreated allograft recipients. Additionally, thymic apoptosis was found by in situ DNA end labeling and electron microscopy. Apoptotic cells were predominantly distributed in the cortex. Biologic lymphotoxin (tumor necrosis factor-beta)/tumor necrosis factor-alpha cytotoxic activity in the serum was significantly increased in untreated hepatic allograft recipients. Tumor necrosis factor-beta mRNA was detected in untreated allograft livers, and intraperitoneal administration of recombinant human tumor necrosis factor-beta induced extensive apoptosis of thymocytes in vivo. In contrast, no significant thymic involution was observed in donor-specific blood transfusion-treated allograft and isograft recipients. Intraperitoneal administration of rabbit anti-human tumor necrosis factor-beta polyclonal antibody or recombinant human interleukin-10 inhibited thymic apoptosis in untreated hepatic allograft recipients.

CONCLUSIONS

Allograft rejection, but not donor-specific transfusion-induced immunologic unresponsiveness, is associated with thymic involution, a process that may be mediated by tumor necrosis factor-beta.

Interleukin (IL)-4-independent induction of immunoglobulin (Ig)E, and perturbation of T cell development in transgenic mice expressing IL-13

Recent studies using interleukin (IL)-4-deficient animals have highlighted the existence of IL-4-independent immunoglobulin (Ig)E induction. We have established transgenic mice expressing IL-13 from a transgene comprising a genomic fragment containing the IL-13 gene and the human CD2 locus control region. The transgenes were expressed in lymphoid tissues and induced by T cell activators, suggesting regulation by elements of the IL-13 promoter. IL-13 transgenic lines expressed 10-100-fold higher levels of serum IgE than their littermate controls, but had normal levels of other serum Ig isotypes. Elevated IgE levels were also detected in sera from IL-4-deficient mice carrying IL-13 transgenes, indicating that IL-4 is not required for IL-13-induced IgE expression in the mouse. Expression of IL-13 also perturbed the development of thymocytes. Although thymocyte development was normal up to 4 wk of age, thymocyte number decreased dramatically thereafter, reaching 10% of normal by 10 wk, and despite normal size and appearance, histological examination demonstrated that transgenic thymi contained only small foci of thymocytes. The reduction in thymocyte number was due mainly to a depletion of CD4(+)CD8(+) thymocytes, and did not affect significantly the composition of peripheral T cell populations. These data indicate that expression of IL-13 transgenes in vivo can regulate IgE production in the mouse, and that IL-13 may also influence thymocyte development.

Differentiation of forbidden T cell clones and granulocytes in the parenchymal space of the liver in mice treated with estrogen

Estrogen was administered to B6 (NK1.1+ strain), BALB/c (Mls-1b2a, V beta 3+ cells being forbidden clone), or (B6 x BALB/c) F1 mice (1 mg/mouse). On days 3 and 10, the number of cells yielded by the liver doubled, whereas that yielded by the thymus decreased prominently. The numbers of cells in the spleen, bone marrow, and blood were unchanged. c-kit+ stem cells, which give rise to multilineage cells, were present in the liver and bone marrow. The proportion of such c-kit+ cells in the liver increased while that in the bone marrow decreased on day 3. Therefore, the absolute number of c-kit+ stem cells increased severalfold in the liver and clusters of lymphoid cells became visible in the parenchymal space. At that time, the expression of recombination activating gene-1 and -2 mRNAs became prominent. Reflecting these phenomena, the number and proportion of IL-2R beta+ CD3int cells (i.e., primordial T cells) increased in the liver on days 3 and 10. An increase in the number of proportion of such CD3int cells was seen even in the thymus and uterus. In parallel with the increase of CD3int cells, the proportion of granulocytes also increased in various organs on day 3. Forbidden clones were present in either the NK1.1+ or the NK1.1- subset of CD3int cells in (B6 x BALB/c) F1 mice treated with estrogen and liver mononuclear cells in such mice acquired potent cytotoxicity against syngeneic thymocytes. These results reveal that estrogen has the ability to potentiate the generation of self-reactive T cells and granulocytes in the liver and other organs.

Gonadectomy impairs lymphocyte proliferation and macrophage function in male and female rats. Correlation with key enzyme activities of glucose and glutamine metabolism

The effect of gonadectomy on lymphocyte proliferation and macrophage function (hydrogen peroxide production and phagocytosis capacity) of male and female rats was examined and the results correlated with the activities of hexokinase, glucose-6-phosphate dehydrogenase, citrate synthase and phosphate-dependent glutaminase. Also, the reversion of the changes by the treatment with oestrogen or progesterone or a combination of both was addressed. Taken as a whole, ovariectomy reduced hydrogen peroxide production and phagocytosis capacity by macrophages and also lymphocyte proliferation. Castration of male rats reduced the proliferation of lymphocytes and raised macrophage phagocytosis capacity. The effects on macrophage function were correlated with changes in glucose metabolism, particularly, in the activity of glucose-6-phosphate dehydrogenase.

Lymphocyte protein synthesis: evidence that murine T cells are more affected by stress than B cells

B and T cells present in the spleen and other sites of the immune system play a crucial role in the protection of individuals by mounting a specific primary and secondary immune response. Disturbances in their signaling and functioning could lead to a deterioration of the defense mechanisms and thereby lead to infections, pathologies or diseases. In this work, we studied the effects of stress on the protein synthesis and metabolism of mouse splenocytes. The study was done by radiolabeling the entire mouse with 35S-methionine (in vivo procedure) or by culturing spleen cells under various conditions of stimulation in the presence of 35S-methionine (in vitro labeling). The stimulus was lipopolysaccharide (LPS), LPS + interleukin-4 (IL-4) and concanavalin A (on A). Samples from immobilization stressed and control animals were studied in parallel. The results showed minimum alterations due to stress on B cells, though a small decrease in proliferative capacity was observed. In contrast, T cells are profoundly affected by stress. More than 100 new proteins are expressed on 2D-gel patterns of T cells from stressed animals as compared with controls, some of which could be implicated in different signaling, or could have appeared because of an alteration in a pathway of synthesis, or even as a consequence of a change in the composition of T cell populations induced by stress.

Origin of CD57+ T cells which increase at tumour sites in patients with colorectal cancer

Human T cells carrying natural killer (NK) markers, CD57 or CD56 antigens, appear to be distinguishable from other T cell subsets in terms of their granular lymphocyte morphology and their numerical increase in patients with AIDS and in recipients of bone marrow transplantation. At the beginning of this study, we observed that CD57+ T cells as well as CD56+ T cells were abundant at tumour sites in many patients with colorectal cancer. Since all these findings for CD57+ T cells are quite similar to those of extrathymic T cells seen in mice, we investigated how CD57+ T cells are distributed to various immune organs in humans. They were found to be present mainly in the bone marrow and liver, but to be completely absent in the thymus. Similar to the case of extrathymic T cells in mice, they were observed to consist of double-negative CD4-8- subsets as well as single-positive subsets (preponderance of CD8+ cells), and to contain a considerable proportion of gamma delta T cells. These features are striking when compared with those of CD57- T cells, which are characterized by an abundance of CD4+ subsets and alpha beta T cells. Not only at tumour sites but also in the peripheral blood, some patients with colorectal cancer displayed elevated levels of CD57+ cells. These results suggest that CD57+ T cells may be of extrathymic origin, possibly originating in the bone marrow and liver, and may be associated with tumour immunity, similar to another extrathymic population of CD56+ T cells in humans.

Deregulated T cell activation and autoimmunity in mice lacking interleukin-2 receptor beta

In mice lacking the interleukin-2 receptor beta chain (IL-2R beta), T cells were shown to be spontaneously activated, resulting in exhaustive differentiation of B cells into plasma cells and the appearance of high serum concentrations of immunoglobulins G1 and E as well as autoantibodies that cause hemolytic anemia. Marked infiltrative granulocytopoiesis was also apparent, and the animals died after about 12 weeks. Depletion of CD4+ T cells in mutant mice rescued B cells without reversion of granulocyte abnormalities. T cells did not proliferate in response to polyclonal activators, nor could antigen-specific immune responses be elicited. Thus, IL-2R beta is required to keep the activation programs of T cells under control, to maintain homeostasis, and to prevent autoimmunity.

Androgen regulation of intra-and extra-thymic T cells and its effect on sex differences in the immune system

Male predominance of malignant disease and female predominance of autoimmune diseases is widely known in humans. To elucidate one of the underlying mechanisms, we examined whether sex differences exist at the level of extra-thymic T cells in various organs of mice under physiological conditions. Effects of castration and testosterone administration were also examined. Intra- and extra-thymic T cells with T cell receptors (TCR) of bright and intermediate intensities, respectively, and with nil and high levels of the interleukin-2 receptor beta-chain respectively, were identified by immunofluorescence. Of the three strains tested, it was demonstrated that intermediate TCR cells were predominant in the liver of female mice. In the liver of male mice after bilateral orchidectomy, mononuclear cells increased and intermediate TCR cells predominated as if they were female; testosterone treatment prevented this immunological consequence of orchidectomy. As extra-thymic T cells comprise a considerable proportion of self-reactive forbidden clones and possess cytotoxic activity against syngeneic tumour cells, the present results suggest a possible relationship between (a) physiologically low levels of extra-thymic T cells in males and the male predominance of malignancy, and (b) the high levels of extra-thymic T cells in females and female predominance of autoimmune diseases.

In vivo CD3+CD25+ lymphocyte subpopulation is down-regulated without increased serum-soluble interleukin-2 receptor (sIL-2R) by gonadotropin releasing hormone agonist (GnRH-a)

PROBLEM

To test further whether the suppression of the CD3+CD25+ lymphocyte subpopulation by gonadotropin-releasing hormone agonist (GnRH-a) is related to the change in levels of cytokines and soluble interleukin-2 receptor (sIL-2R).

METHOD

Twenty-seven infertile patients were enrolled under the long protocol of GnRH-a agonist (buserelin acetate) and superovulation with gonadotropin from our IVF-ET program. Peripheral B cells, NK cells, CD4+ and CD8+ T cells and the expression of CD69, CD25, HLA-DR, and CD71 antigens on the T cells were serially examined by dual-color flow cytometry. Serum levels of cytokines and sIL-2R were measured.

RESULTS

The B cells, NK cells, T cells, CD4+, CD8+ T cells, CD3+DR+, and CD3+CD71+ lymphocyte subpopulations were not changed after the use of GnRH-a. The CD25+ T cell subpopulation was significantly down-regulated, but the CD69+ T cell subpopulation was increased when the GnRH-a was used for approximately 2 wk. The serum levels of interleukin-1 beta (IL-1 beta), interleukin-2 (IL-2), interleukin-4 (IL-4), interferon-gamma (IFN-gamma), and sIL-2R were not changed.

CONCLUSION

The GnRH-a had a transiently suppressive effect on CD25+ T cells, but a stimulatory effect on CD69+ T cells. However, the serum level of cytokines or sIL-2R did not change. These immunological modulations seems to be the result of interaction between GnRH-a and estrogen.

Increase in the proportion of granulated CD56+ T cells in patients with malignancy

Evidence is presented for the existence of a unique T cell population which expressed one of the natural killer (NK) markers, CD56 antigen, in humans. Although such CD56+ T cells were a minor population in the peripheral blood (< 10%), they were abundant in the liver (up to 50%), which was recently demonstrated to be a major organ for extrathymic T cell differentiation in mice. As in the case of extrathymic T cells in mice, these CD56+ T cells in humans contained a higher proportion of gamma delta T cells than did CD56- T cells, contained double-negative CD4-8- cells, and had the morphology of large granular lymphocytes. This unique population of CD56+ T cells tended to be elevated in the blood and among tumour-infiltrating lymphocytes in patients with colorectal cancer, especially in advanced cases. These results raise the possibility that, as in mice, CD56+ T cells with extrathymic T cell properties may also be associated with tumour immunity in humans.